/*
 * Created on 21-Mar-2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.util;

import java.io.File;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.gudy.azureus2.core3.util.Debug;

public class LinkFileMap {
    /*
     * History here: Before 5001_B22 file linkage was performed by linking source files and target files - source file being the original, unmodified
     * location of the file as if no linking had been performed, target being wherever. This was designed way back when the FileManager didn't have
     * any knowledge of torrents and therefore didn't understand what a file index within a torrent was and it just applied a source->target renaming
     * operation transparently. However, things changed and torrent knowledge crept into the FileManager (for piece-reordering storage for example).
     * Linking was still based on file though. Then a bug appeared caused by the removal of OS-specific illegal file system chars (e.g. : on windows)
     * resulting in two files in the torrent resolving to the same physical file on disk. The 'obvious' solution, to rename one of them to avoid the
     * conflict, didn't work as renaming is based on linking and linking was based on physical file names, and both files had the same physical file
     * so the rename affected both files and left the conflict in existence. So I decided to rework the code to use file indexes instead of source
     * file names. Well, I currently have both in place to support migration of config, but at some point we should be able to remove the source-file
     * component of linking and just use index->target. Maybe Note that the FileManagerImpl's getLink requires access to the from-name to verify that
     * the link it looks up is valid (principally caused by the 'move' method running BEFORE links are updated - really this should be reworked
     */

    private Map<wrapper, Entry> name_map = new HashMap<wrapper, Entry>();
    private Map<Integer, Entry> index_map = new HashMap<Integer, Entry>();

    public File get(int index, File from_file) {
        if (index >= 0) {

            Entry entry = index_map.get(index);

            if (entry != null) {

                return (entry.getToFile());
            }
        } else {

            Debug.out("unexpected index");
        }

        Entry entry = name_map.get(new wrapper(from_file));

        if (entry == null) {

            return (null);

        } else {

            // migration - all existing links to migrate have an index of -1

            int e_index = entry.getIndex();

            if (e_index >= 0 && e_index != index) {

                return (null);
            }

            return (entry.getToFile());
        }
    }

    public Entry getEntry(int index, File from_file) {
        if (index >= 0) {

            Entry entry = index_map.get(index);

            if (entry != null) {

                return (entry);
            }
        } else {

            Debug.out("unexpected index");
        }

        Entry entry = name_map.get(new wrapper(from_file));

        if (entry == null) {

            return (null);

        } else {

            // migration - all existing links to migrate have an index of -1

            int e_index = entry.getIndex();

            if (e_index >= 0 && e_index != index) {

                return (null);
            }

            return (entry);
        }
    }

    public void put(int index, File from_file, File to_file) {
        Entry entry = new Entry(index, from_file, to_file);

        if (index >= 0) {

            index_map.put(index, entry);

            // remove any legacy entry

            if (name_map.size() > 0) {

                name_map.remove(new wrapper(from_file));
            }
        } else {

            wrapper wrap = new wrapper(from_file);

            Entry existing = name_map.get(wrap);

            if (existing == null || !existing.getFromFile().equals(from_file) || !existing.getToFile().equals(to_file)) {

                Debug.out("unexpected index");
            }

            name_map.put(wrap, entry);
        }
    }

    public void putMigration(File from_file, File to_file) {
        Entry entry = new Entry(-1, from_file, to_file);

        name_map.put(new wrapper(from_file), entry);
    }

    public void remove(int index, File key) {
        if (index >= 0) {

            index_map.remove(index);

        } else {
            // this can happen when removing non-resolved entries, not a problem
            // Debug.out( "unexpected index" );
        }

        if (name_map.size() > 0) {

            name_map.remove(new wrapper(key));
        }
    }

    public Iterator<Entry> entryIterator() {
        if (index_map.size() > 0) {

            if (name_map.size() == 0) {

                return (index_map.values().iterator());
            }

            Set<Entry> entries = new HashSet<Entry>(index_map.values());

            entries.addAll(name_map.values());

            return (entries.iterator());
        }

        return (name_map.values().iterator());
    }

    public String getString() {
        String str = "";

        if (index_map.size() > 0) {

            String i_str = "";

            for (Entry e : index_map.values()) {

                i_str += (i_str.length() == 0 ? "" : ", ") + e.getString();
            }

            str += "i_map={ " + i_str + " }";
        }

        if (name_map.size() > 0) {

            String n_str = "";

            for (Entry e : name_map.values()) {

                n_str += (n_str.length() == 0 ? "" : ", ") + e.getString();
            }

            str += "n_map={ " + n_str + " }";
        }

        return (str);
    }

    public static class Entry {
        private int index;
        private File from_file;
        private File to_file;

        private Entry(int _index, File _from_file, File _to_file) {
            index = _index;
            from_file = _from_file;
            to_file = _to_file;
        }

        public int getIndex() {
            return (index);
        }

        public File getFromFile() {
            return (from_file);
        }

        public File getToFile() {
            return (to_file);
        }

        public String getString() {
            return (index + ": " + from_file + " -> " + to_file);
        }
    }

    private static class wrapper {
        private String file_str;

        protected wrapper(File file) {
            file_str = file.toString();
        }

        public boolean equals(Object other) {
            if (other instanceof wrapper) {

                return (file_str.equals(((wrapper) other).file_str));
            }

            return (false);
        }

        public int hashCode() {
            return (file_str.hashCode());
        }
    }
}
